vertically misaligning vestibular reflex

Perception of the spatial vertical is important for maintaining and stabilizing vertical posture during body motion. The velocity storage pathway of vestibulo-ocular reflex (VOR), which integrates vestibular, optokinetic, and proprioception in the vestibular nuclei vestibular-only (VO) neurons, has spatio-temporal properties that are defined by eigenvalues and eigenvectors of its system matrix. The yaw, pitch and roll eigenvectors are normally aligned with the spatial vertical and corresponding head axes. Misalignment of the roll eigenvector with the head axes was hypothesized to be an important contributor to the oscillating vertigo during MdDS...

Sudden unilateral loss of vestibular afferent input causes nystagmus, ocular misalignment, postural instability and vertigo, all of which improve significantly over the first few days after injury through a process called vestibular compensation (VC). Efferent neuronal signals to the labyrinth are thought to be required for VC. To better understand efferent contributions to VC, we compared the time course of VC in wild-type (WT) mice and α9 knockout (α9(-/-)) mice, the latter lacking the α9 subunit of nicotinic acetylcholine receptors (nAChRs), which is thought to represent one signaling arm activated by the efferent vestibular system (EVS)...

INTRODUCTION: Vertigo and dizziness are common neurological symptoms in general practice. Most patients have benign peripheral vestibular disorders, but some have dangerous central causes. Recent research has shown that bedside oculomotor examinations accurately discriminate central from peripheral lesions in those with new, acute, continuous vertigo/dizziness with nausea/vomiting, gait unsteadiness, and nystagmus, known as the acute vestibular syndrome. CASE REPORT: A 56-year-old man presented to the emergency department with acute vestibular syndrome for 1 week...

UNLABELLED: The vestibular organ is a sensor that measures angular and linear accelerations with six degrees of freedom (6DF). Complete or partial defects in the vestibular organ results in mild to severe equilibrium problems, such as vertigo, dizziness, oscillopsia, gait unsteadiness nausea and/or vomiting. A good and frequently used measure to quantify gaze stabilization is the gain, which is defined as the magnitude of compensatory eye movements with respect to imposed head movements...

PURPOSE: This article considers vertical misalignment and torsion of the eyes that arise from disorders of vestibulo-ocular reflex (VOR) pathways. RECENT FINDINGS: Infarction of the nodulus is one of the causes of skew deviation, a vertical strabismus accompanied by torsion of the eyes and tilt of the subjective visual vertical. Vertical components of childhood strabismus may arise from dysgenesis of vestibular projections in the brainstem. If vertical misalignment decreases greatly in the supine position compared to the erect poison one may conclude that skew deviation rather than a fourth nerve palsy is responsible for the strabismus...

The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibulo-ocular response...

BACKGROUND AND PURPOSE: Acute vestibular syndrome (AVS) is often due to vestibular neuritis but can result from vertebrobasilar strokes. Misdiagnosis of posterior fossa infarcts in emergency care settings is frequent. Bedside oculomotor findings may reliably identify stroke in AVS, but prospective studies have been lacking. METHODS: The authors conducted a prospective, cross-sectional study at an academic hospital. Consecutive patients with AVS (vertigo, nystagmus, nausea/vomiting, head-motion intolerance, unsteady gait) with >or=1 stroke risk factor underwent structured examination, including horizontal head impulse test of vestibulo-ocular reflex function, observation of nystagmus in different gaze positions, and prism cross-cover test of ocular alignment...

The angular vestibulo-ocular reflex (aVOR) has a fast pathway, which mediates compensatory eye movements, and a slow (velocity storage) pathway, which determines its low frequency characteristics and orients eye velocity toward gravity. We have proposed that motion sickness is generated through velocity storage, when its orientation vector, which lies close to the gravitational vertical, is misaligned with eye velocity during head motion. The duration of the misalignment, determined by the dominant time constant of velocity storage, causes the buildup of motion sickness...

The responses of vestibulospinal neurons to 0.5-Hz, whole-body rotations in three-dimensional space and static tilts of whole-body position were studied in decerebrate and alert cats. The neurons' spatial properties for earth-vertical rotations were characterized by maximum and minimum sensitivity vectors (R(max) and R(min)) in the cat's horizontal plane. The orientation of a neuron's R(max) was not consistently related to the orientation of its maximum sensitivity vector for static tilts (T(max)). The angular difference between R(max) and T(max) was widely distributed between 0 degrees and 150 degrees, and R(max) and T(max) were aligned (i...

1. We studied the three-dimensional input-output human vestibuloocular reflex (VOR) kinematics after selective loss of semicircular canal (SCC) function either through total unilateral vestibular deafferentation (uVD) or through single posterior SCC occlusion (uPCO), and showed large deficits in magnitude and direction in response to high-acceleration head rotations (head "impulses"). 2. A head impulse is a passive, unpredictable, high-acceleration (3,000-4,000 degrees/s2) head rotation through an amplitude of 10-20 degrees in roll, pitch, or yaw...

To investigate the neural substrate of vestibulo-sympathetic reflexes, we studied the responses of neurons in the rostral ventrolateral medulla (RVLM) of decerebrate cats to natural stimulation of the labyrinth in vertical and horizontal planes. The RVLM is a major source of excitatory inputs to sympathetic preganglionic neurons. The animals used in these studies were baroreceptor-denervated and vagotomized and had a cervical spinal transection so that inputs from tilt-sensitive receptors outside of the labyrinth did not influence the units we recorded...

1. This series of three papers aims to describe the three-dimensional, kinematic input-output relations of the rotational vestibuloocular reflex (VOR) in humans, and to identify the functional advantages of these relations. In this first paper the response to sinusoidal rotation in darkness at 0.3 Hz, maximum speed 37.5%/s, was quantified by the use of the three-dimensional analogue of VOR gain: a 3 x 3 matrix where each element describes the dependence of one component (torsional, vertical, or horizontal) of eye velocity on one component of head velocity...

Second-order vestibular nucleus neurons which were antidromically activated from the region of the oculomotor nucleus (second-order vestibuloocular relay neurons) were studied in alert cats during whole-body rotations in many horizontal and vertical planes. Sinusoidal rotation elicited sinusoidal modulation of firing rates except during rotation in a clearly defined null plane. Response gain (spike/s/deg/s) varied as a cosine function of the orientation of the cat with respect to a horizontal rotation axis, and phases were near that of head velocity, suggesting linear summation of canal inputs...